Communication system



y 1-, 1934. c. A. PORTMAN 1,957,288

commumcmmn SYSTEM Filed June 19, 1930 a o- (2000 77 i n Receiver INV ENTOR C/emeni A. for/mcm A'TTORNEY Patented May 1, 1934' stars PATENT OFFICE COMMUNICATION SYSTEM Application June 19,. 1930, Serial No. 462,192

2 Claims.-

My invention relates tocommunication systems in general but more particularly to a carrier-current telephone system wherein a plurality of transmitting and receiving stations are ca- -pacitatively coupled to a common communication channel, usually a power-line circuit or other similar wired systems.

Previous to my invention, an operator of a carrier-current telephone, when calling another station, had no means of knowing whether the call had been properly received until the party at the called station had answered by removing the receiver from the hook.

During summer seasons, when static is prevalent, or when unusual line noises are present, the

selectors of a carrier telephone are frequently in the state of constant agitation. This often prevents a call from registering. When this condition exists, it is necessary for the calling party to repeat the dialing operation, perhaps several times, and wait a reasonable period after each attempt in order to give the party at the called station time to answer the phone. In the event that the call is not properly received and does not operate the signal at the receiving end, the calling party has no knowledge of the fact until after the lapse of an .unreasonable interval of time. This results in a loss of valuable time, especially in a case of emergency.

Furthermore, in carrier-current telephone installations, more particularly those wherein transmission and reception are carried on at different frequencies, a lockout circuit is provided to prevent interference from any of the stations when two stations are in a position for communication. The limitation of this installation at present is that it does not prevent interference during the interval between the calling operation and the answering of the call, during which interval other stations are adapted to tie in on the line' and cause confusion in dialed signals.

It is one object of my invention to provide means for indicating to the calling party the condition of the signalling means at the called station, more particularly to acquaint the dialing party of the fact that the dialed impulses have registered at the receiving station and have caused the actuation of the signalling or calling means.

Another feature of my invention is to accomplish the above result simultaneously with the operation of the calling means.

A further object is to provide means for locking out from the system all receiving stations except the called station by the time the dialedimpulses register at the receiving station.

Other objects and. features of my invention will be disclosed in the following description, taken in connection with the accompanying 69 drawing, wherein Figure 1 is a combined schematic and diagrammatic disclosure of a part of a carrier-current telephone system of the type referred to above" and embodying my invention; and r Fig. 2 represents schematically a complete system of the type described.

The system, as disclosed in Fig. 1, shows only two stations A and B coupled capacitatively to a common communicating channel 1. This is done, however, only for the purpose of simplifying the explanation of the system, it being apparent that any'num'ber of parties may be coupled to the same communication channel, as illustrated in Fig. 2.

Station A, represented by phone A and it's associated' call selector transmitter and receiver, is illustrated in block form in the upper righthand portion of the drawing. The transmitter is tuned to one frequency, e. g., 60,000 and the receiver to a different frequency, e. g., 50,000 The remainder of the drawing relates to station B, the transmitter and receiver of which are illustrated in block form, the call selector and phone circuit of which being repre- 35 sented diagrammatically for the purpose of clear- 1y illustrating the operation and functions of my invention.

The receiver at station E adjusted to receive at 60,000 is shown connected, by means of relay armatures 2 and 3, to the primary 4- of a transformer coupling, the secondary 5 of which constitutes the input means to a detector circuit 6, in the plate circuit of which is placed a relay '7.

An armature 8, associated with the relay '7, is connected-to ground andis adapted, upon the deenergization of the relay, to close a circuit through a relay 9, the circuit through said relay being grounded through a source of potential 11". A grounded armature 12, associated with the relay 9, is adapted to close either of two circuits by means of front and back contacts 13 and 14, respectively. The front contact completes a circuit, through the slow-acting relay 16, to ground through the source of potential 23, the back contact at 14 putting ground potential on the contact 17 associated with the slow-acting relay 16. Another armature 10 is adapted to put ground upon all contacts of the selector bank A, except 0 contact 15, which corresponds to the station number. Relay 16 will operate to attract armature 18 to nake contact with the terminal 17, thereby completing a circuit through the relay 19 and the relay 20 by means, of the conductors 21 and 22, respectively, the batteries 25 and 24, respectively, and connections to ground. The relay 20, termed the motorrelay, is adapted to operate a plurality of selector banks A, B and C, all mounted on the same shaft. 7 '7 The slow-acting relay 19 has an armature 2'7 associated with it that is grounded through the conductor 28. In its deenergized condition, the armature 2'7 will close a circuit through conductor 29, thereby putting ground potential on the selector arms ofthe B and C banks. When relay 19 is in its energized condition, the armature 27 is adapted to complete the relay circuit through contact 31, said circuit extending from ground, through said armature, line 32 and relay 33, to ground through the battery 34.

Connection 35 may be one of the contacts on bank B corresponding to the call number or" the station, this connection being extended to the armature 36 associated with the slow-acting relay 83 through conductor 37, the arinature of said relay being adapted to make contact at this point when said relay is in a deenergized condition, thereby completing a circuit, through conductor 33, to the relay 39 and back to ground through the battery 40. The relay 39 is also of the slow-acting type and is capable upon being energized, of attracting the armature 41 associated therewith to close the circuit through the transmitter in such manner as to set the transmitter into operation. n e

A connection 42 on bank C corresponding to that of bank B, is made by means of a circuit over line 96 through the relay 43. This relay, on being energized, will actuate a pair of armatures, one of which, 45, is grounded, and the other or" which, 44, is connected to a signalling means 46 through a condenser 47. The grounded armature 45, upon being attracted by the relay 43, will close the circuit, through conductor 49, the armature 50 of relay 51 and the relay 52, to ground through the source of potential 53.

The other armature 44, associated with'the relay 43, is adapted to fluctuate between a pair of contacts 54 and 55, one contact being connected electrically to the relay 59 and to a contact 60 associated with the relay 58, and the other contact being electrically connected, by means of the conductor 56, to an armature 57 associated with the relay 58.

The relay 52,-in its energized state, is adapted to actuate a pair of armatures 61 and 62 to complete a circuit from a 110-volt, cycle source across the primary 63 of the bell-ringing trans" former. The circuit through the secondary 65 of the transformer may be traced from the ground connection at 64 through conductors 66 and 67, through the signalling means 46 and the condenser 4'7, conductor 48, the contact 55 associated with the relay 43, the back contact 68, associated with the relay 58, through the transformer winding 65, back to ground by way of the bypass condenser 69 and the battery '70, The relay 51, being of high impedance, is not adapted to pass the (SO-cycle frequency which accounts for the bypass condenser 69. A grounded armature 97, associated with the relay 51, will, upon being actuated by said relay, complete a circuit through the relay 58.

The dial impulse contacts '71 and the microphone '72 are serially connected between the com denser 47and the receiver-supporting lever'73 and function to shunt out the signalling means 46 upon the lifting of the receiver '74, which will permit the supporting lever '73 to make contact at the terminal 75. The supporting lever '73 is also so constructed asto make contact at the terminal '76, placing the receiver in electrical connection with the contacts '7'? and 78 through conductors '79 and 80.;

In parallel connection with the relay 59, is the transmitter of station E which is capacitatively coupled to the common communication channel 1 and is tuned to transmit at a frequency of 50,000 to correspond to the receiving frequency of station A. Associated with the relay 59 is an armature 81 groundedthrough conductor 82, said armature, upon energization of the relay 59, being actuated to close the circuit through the contact 83, line 84, the armature 85 associated with the relay 86 and, through the transmitter-controlling relay 39, back to ground through the battery 40. The contact at 85 is adapted to be opened upon the energization of the relay 86. This relay is connected in a circuit which may be traced from the contact arm of the bank A, through the relay 86 and the battery 88, to ground. An armature 92, grounded through conductor 93, is adapted to be actuated, upon the energization of the relay 39, to close a circuit at the contact 94fthrough a relay 95 which is adapted to simultaneously control the operation of the armatures 2 and 3, thereby to disconnect the primary 4 of the transformer and make connection at the contacts 77 and 78, whereby the,,phone B may be placed in the receiving circuit.

in Fig. 2, a complete system is disclosed wherein stations A and C are adapted to transmit at 60,600 and to receive at 50,000 whereas stations B and D are tuned to 50,060 M for transmitting and 60,000 for receiving. Means may be provided at each station for switching frequencies, if desired.

The operation of my invention, as embodied in a system of the above described type, may be explained as follows: i

It will be assumed, for purposes of explanation, that station A is calling station E. The operator of station A will lift his receiver, which will set 7 his transmitter functioning to impress a 60,000 cycle frequency upon the communication channel 1. This carrier current will be received by all stations adapted to receive at this frequency and will serve to decrease the plate current of the detector tube 6 of station B, thereby deenergizing relay 7, permitting the armature 8 to drop back and place ground connection on the relay 9. The same results will occur in the other stations, such'as station receiving at 60,000 cycles. The

energization of relay 9 will pull in armature 10, Q

thus putting ground on all the contacts 'of the A bank except contact 15, which corresponds to the number of station 13. A complete circuit may now be traced from ground, through the armature 10 the contacts of the A bank, except 15, through the contact arm and relay 86, to ground through the battery 88, thereby energizing the relay 86 which" will cause the actuation of the armature 85 to open the circuit at the"motor 'rnagnet;20 at point l'lf Upon dialing the station number of -sta'tion B, which, in this case, is assumed to be 'number'll, the carrier 'currentfrom'the transmitter station A will be interrupted seven times. E'ach'inter nip-tion of the carrier" current will permit the plate current of the detector tube to increase to; its normal value, which is sufficient to energize the relay 7' and thereby break the circuit through the relay 9, thus causing said relay t-o 'b'ecome deenergized. This will permit armatur'e'12' to fall back to complete the circuit through the motor magnet and the relay 19 ,ther'eby" caus-E ing the contact arms ofthe '-A, and C -banks to notch'up one contact, and also causing armature 27 to operate to complete a circuit through the slow-acting relay 33. The energization of the relay 33 will pull in the armature 36.

After receipt of the desired number of interruptions, the circuit through the relay 9 of station B, and the corresponding circuits of all stations receiving on the same carrier current will acircuitthrough the slow acti'ng relay 19 and remain closed. This will result in the relays of all those stations, corresponding to relay 86 of station B, remaining energized, thereby maintaining an open circuit at points corresponding to 85 of station B. It will thus be seen that, at this stage, all stations, except station B, which are adapted to receive on a 60,000 cycle will be locked out from the system. In the meantime, the armature 2'? associated with the relay 19, upon the deenergization of said relay, will complete a circuit, through the bank B by way of conductor 29,

- the contact arm conductors 37 and 38, through relay 39, toground, through the battery 40, thereby energizing said relay, resulting in the operation of the armature 41, thereby causing the transmitter to be set in operation.

The carrier Wave of station B will, consequently, be impressed upon the communication channel 1, the effect of the carrier wave being to produce an audible signal at station A and also to lock out all stations receiving on 50,000 as represented by station C of Fig. 2, in the same manner as the others. The deenergization of the relay 19 will also result in the armature 27 completing a circuit through the bank C, which may be termed the ringing bank, by way of conductor 29, the

contact arm, the relay 43, through battery, to ground' The relay will thus become energized to pull in the armatures 44 and 45 associated therewith. A circuit will thereby be completed from round, through the armature 45 and the relay 52, back to ground through the source of potenthrough conductors 66 and 67, through the signal means 46, the condenser 47, conductor 48, the armature 44, associated with the relay 43, through the secondary winding and the bypass condenser 69, back to ground through the battery 70. This will result in the operation of the signalling means simultaneously with the functioning of the transmitter.

The operator of station E, upon hearing the signalling means, will lift the receiver, thereby permitting the supporting lever to make contact at the point '75 to cause the signalling means to be" shunted by the "serially-connected dialing means-'71 and the microphone 72-5- This will provide a direct-current path throughth'e relay 51', which may be traced from ground, through the eonductors 66 and 6'7, the microphone '72 and dialing. means 71,, through thesecondary of the bell-ringing transformer, through the relay 51 and the battery .70., :to ground.-v The relay 51 will become energized. and attract the-armature 97, thereby closing the circuitthrough the relay 58 which will also b'ecome energized andcause the armature to shiftfro'm the contact 68 to the. con-'- tact 60. l m v The -ener'gization of therel'ay 51. will.v also" break-the circuitat the point 50,- through the relay 52,10 cause-said relay-to become deener-giz'ed' and permit the circuit to the bell-ringing transformer to be broken. The shifting of the armature from the contact 68 to the contact 60 will complete a circuit through the relay 59 from ground through conductor 66, microphone 72 and dial mechanism '71, through conductor 56, the contact 60, through the relay 59 and back to ground, causing said relay to'pull in the armature 81, thereby placing ground connection through the contact 83 upon the relay 39 back to ground.

The voice currents produced by the operator speaking into the microphone 72 are bypassed around the relay 59 by means of conductors 99 and 100 and so react on the transmitting system to modulate the carrier wave sent out upon the communication channel.

It will thus be seen that, in the system disclosed, very useful results are obtained. As soon as the signalling means are caused to be actuated by the dialed impulses, an indication is transmitted over the line back to the calling party, notifying him that his call had been put through and that the signal has been completed.

Under certain conditions, as stated above, very often the dialed impulses do not register at the receiving station, in which case, the resultant absence of the return carrier wave will serve as an indication of the fact that the dialed impulses did not register at the receiving end, thus permitting the calling party to re-dial without the necessity of waiting an unreasonable length of time to determine whether his call has registered.

It will also be noted, as an important feature of this invention, that, upon the successful completion of the calling signal, all other stations in the system are locked out, thereby absolutely preventing them from breaking in upon the system and interfering with the operation of the stations on the line. It will further be noted that this function takes place immediately upon the completion of the call signal and constitutes a great improvement over those systems wherein the locking-out function takes place only upon the lifting of the receiver at the receiving station in answer to a call.

Another function of my invention is that it enables an operator at the master station to dial the various stations in the system and determine the condition of the ringing or signalling systems at the various points.

While my invention has been disclosed as embodied in a system of a particular type, it possesses general adaptations and might be utilized in communication systems in general or in systems wherein indications as to operation of apparatus is desired, and, while it has been described in detail in the above description, I do not desire to be limited to such detail except insofar as the invention is limited by the prior art and the appended claims.

I claim as my invention:

' l. A communication system comprising a plurality of transmitting circuits, a plurality of similar receiving circuits tuned to receive at the same frequency, one of said transmitting circuits being associated with each of said receiving circuits, means for selectively dispatching a call signal to any one of said receiving circuits, and means controlled by the received signal at the selected station for causing the transmitter at said station to transmit to the dispatching end a signal indicating the completion of the call at the receiving end and means also controlled by said received signal for signalling the called party. 2. In a communication system, a plurality of transmitting circuits, a plurality of receiving circuits tuned to receive at the same frequency one of said transmitting circuits being associated with each of said receiving circuits, means for dispatching a signal to any one of said receiving circuits to the exclusion of the others, and means controlled by the received signal at the selected station for causing the transmitter at said station to transmit to the dispatching end a signal indicating the completion of the call at the receiving end and means also controlled by said received signal for signalling the called party, both of said means operating simultaneously. CLEMENT A. PORTMAN. 

